View Full Version : Dam that will not hold water
I have recently purchased a property at Ocean View in QLD and there is a large dam down the back that will not hold water. The soil is a beautifull red volcanic sort of soil but just does not seem to hold water. I am looking for a cheap way of fixing it. It is a huge hole probably about 4 to 5 times the size of your average small dam. If anyone has any ideas that would be great
21-04-2006, 09:54 PM
Some things that come to mind are:
1. Graze cattle or pigs in the dam for a period of time. The manure promotes bacterial growth that helps seal the dam.
2. Bentonite - a fine clay that seals dams. Not cheap I expect.
I'm definitely no expert but search the archives because this topic has been discussed before.
21-04-2006, 11:11 PM
Do you meen feeding in the dam,Its a combintion of poo,animal weight, and compaction that help seel dams
22-04-2006, 12:23 AM
that's interesting, the animal method.
so is that how they start dams off in the first place?
like if i dug out a dam, would i try and fill it and see if it leaks,
or would one just go for the animal method from the word go?
I just thought if you dig a dam it will just work.
22-04-2006, 03:53 AM
From what I hear, volcanic soil dams are the one of the most difficult to seal.
You dig out the dam, then (I believe) you fence it, put some cattle in there, feed them and water them there, and their poo forms a kind of gley that ferments and seals the dam.
Is this a water-catchment dam? If the first run of cattle doesn't seal it enough, do it again.
If the water-holding area can grow plants, you might try growing a fodder-type cover crop like lablab before you let the cattle in. (See http://www.tropicalgrasslands.asn.au/pa ... lablab.htm (http://www.tropicalgrasslands.asn.au/pastures/lablab.htm))
Richard on Maui
22-04-2006, 04:03 AM
Generally you compact your soil with a bulldozer or something heavy that is going to compress all the pore spaces until there is little or no percolation occuring. If your soil is made up of partly unweathered or porous rock, for instance, such as Brad may have with his relatively new (?) volcanic soil, this mightn't be so easy. Depends on the type of clay and the overall clay content.
Bentonite is a clay that expands to many times its particle size when it comes into contact with water, so if the dam isn't too porous, it might work to incorporate a certain amount of bentonite into the bottom of the dam and then compact it a little. You don't juist spread the bentonite around on the surface and then fill er up. Actually, I've read that you need to incorporate bentonite into the construction of the keyway too, which is like the core of the dam wall, depending on the design of the dam and other variables.
I believe that the manurial thing is to do with anaerobic bacteria that form a surface seal, and probably the weight of the animals causes compaction too.
Hope some of my rambling has been helpful, Brad.
thanks for all your replies, to add more detail I estamate the dam would be between 5 - 10 years old and it does have a key way cut in and it does get plenty of run off. There is quite a lot of grass and small trees growing in the bottom and in the wall. It would be approx 15m deep and its deepest point.
I might get a couple of quotes to start with to see how much and how possible it is to get it compacted. I was already planning on getting a cow or 2 to help keep the grass down so if the quotes are no good I will fence off around the dam and put my cows in there for a while, I may as well give it a go. I really want to get the dam fixed, once its full we wil have plenty of water for our animals and plants
22-04-2006, 08:29 AM
Congratulations on your purchase. All the above suggestions are great, I wish to add a couple more.
1. Ask a local farmer, someone who has been around the district for years for their advice. They tend never to offer expensive solutions - contractors do.
2. This is one of my favourite sites now [thanks richard on maui] http://www.vetiver.com and consider this plant both uphill, downhill and across the banks. I saw this plant [even when it was quite small] hold a dam wall together for the first time. I am sad I didnt take photos, this plant did a miraculous job.
3. Consider hiring a self-propelled vibrating roller, either smooth or sheepsfoot for a weekend. They are very simple to operate.
4. Check with the 'farmer' and see if there is underground water available in your area. It may be prudent to put down a bore, they are often a better option than a dam.
22-04-2006, 11:27 AM
To the best of my limited knowledge all earth-built water storage facilities (dams) require a binding agent in the soil 'liner' of the dam. Clay usually does the trick. If you do not have ready access to clay on site then it may have to be imported in. You suggest that there is a 'key' in situ, this is good. I wonder if this was fashioned from clay-type soil found on the site?
The cattle/livestock ideas previously offered all sound very interesting.
Darren Doherty from permaculture.biz is one guy you could talk with about your dam. He's a whiz with this stuff and is a very approachable guy.
Oh, one other point that may be worth considering: Trees growing in the lining of the dam and in the dam wall could be where your storage facility is breaking down. Tree roots, and the subsequent 'drainage lines' that occur as a result of them, may be the cause of your problem (although you state that your trees are only small). Trees should never be grown in the actual dam wall, they can weaken the structure and cause it to fail.
Richard on Maui
22-04-2006, 05:55 PM
absolutely, what mark says. the trees must go. you will never hold water in there while the trees are growing. and, sad to say, once they are gone, the holes left by the decomposed roots that water will find and leak out of... sounds like it might not be too cheap to fix this pond :cry:
22-04-2006, 06:19 PM
yep no trees growing in the dam or particularly on the wall. talk to a local dam builder of note (ask around the farmers will know who is good), some soils just will never hold water adding bentonite or clay to seal the dam could be expensive and may not be guranteed to work.
23-04-2006, 03:02 AM
My little piece of land is as flat as a tabletop, so I don't need a dam, but I have a question anyway:
Can you grow anything on the actual dam? Shrubs, etc? Or is it safe to just grow grass, or even to keep it bare?
Richard on Maui
23-04-2006, 03:23 AM
At Tagari they planted a lot of bamboo on the dam walls to stabilize the soil. Stuff with shallow but extensive root systems would seem to be appropriate. Even small shrubs can have deeper roots, I guess, and if they "fail"; blow over or just die, they are potentially going to take the dam with them. When I was at Tagari I was given the task of going around all the dams and cutting down all the acacias that were springing up on the dam walls. With their live fast/die young antics they were real potential dambusters I suppose.
24-04-2006, 06:35 AM
pretty much only grasses and those woody type flowering plants, things that have fairly shallow root systems not even sure i'd use bamboo but then some of the smaller species maybe ok?
27-04-2006, 09:49 AM
Hey Brad, I'm just going to chuck my 2 cents worth in. I did a stint with farm water advisory a few years ago up in Qld for DNR&M, surveying/building farm dams etc. (At the risk of repeating what everyone else has said!) Ask around and see if you can find who built your dam, most likely it was a local bloke. If it was a Govt department that designed it they may still have the specs on file. (Check with DNR&M if they still do this service) It sounds pretty substantial, so a risk assesment should have been carried out in case of a breach. Your wall should have been built with a clay core compacted with something like a vibrating sheepsfoot roller. The clay itself should have been subject to testing, dispersability etc.
Never allow trees to grow on the wall, in the dam itself, or in the spillway area. The spillway area is where the water will overflow from your dam when it is full. If trees are planted here and you get a fast overflow during a storm event, the water will swirl around the trunks and cause erosion. The spillway should be an even grade, keep it grassed. It shouldn't be a gully! Keep your wall grassed too to prevent erosion. Allowing stock onto the wall is up to you, but keep an eye on erosion effects due to overgrazing, you may want to consider a stock watering point.
I'm afraid it's pretty costly but a clay blanket is probably your best bet in repairing the leaks. But if you can source the material on site that will save a bit of money.
Hope I've helped...not rambled on too much.... :D
27-04-2006, 08:34 PM
Looks as though you have some good experience in this area, (as have others who have contributed here). I've heard the golden rule about no trees on the dam wall. How about small trees beside the dam but not on the wall as such?
Our dam is right near the neighbour's fence, and we're building a pavilion on the other side of the dam with a Chinese style roof, a little fantasy we have nurtured for some years now. I have planted some small native trees to give us a screen from the neighbours house, which otherwise would look straight down on our pavilion. Trees like the lilypily acmena smithii, and one bangalow palm which won't screen much but apparently they like water and they look beautiful. What do you think?
01-05-2006, 09:17 AM
Now flora's not my strong point... I'm a water babe... :) You really don't want the root systems of the trees reaching the wall or the bed of your dam. I don't know how extensive the roots of your trees would be, so if you found that out then that would give you a general idea of how close you could plant. I would err on the side of caution....
btw, sounds really cool. there's a chinese style section in Hunter Valley Gardens where they've done a pavilion and a walkway out into their pond a bit, looks great. you should post a before and after photo, give us quarter acre folks something to dream about :sleepy2:
03-05-2006, 06:13 PM
Ah, our Chinese pavilion. It took a step forward today when the builder put up the eight curved rafters that I spent weeks making. It is starting to get the look, I think (hope) it's going to be spectacular. I'm wrangling with our brilliant builder over whether the corners can be raised in a second curve (apart from the main curve of the roof) at the corners.
I am taking pics as the pavilion goes up, and when I can work out how to post them I will. I know there's a system for putting them on a site and giving the links here, but I'd really like to put them direct into a contribution here. Like Chickadee's magnificent chook house pics (the chook house AND the pics are magnificent). I'll get it worked out eventually.
So watch this space,
Richard on Maui
04-05-2006, 04:28 AM
Look forward to seeing your pics Peter. You know, I had the idea for a pavillion in my mock design on the PDC I did, as a place for reflection and observation, and because I thought it would appeal to "the client". Geoff Lawton, if you are reading this thread, ha ha! YOu poopoohed me about a pavillion didn't you? Look, I'm not the only one who thinks they are cool.
15-05-2006, 05:52 PM
First post to this fantastic forum, just have a couple of comments...
Interesting talk of "sheepsfoot rollers". I've heard that flocks of sheep were used to compact dams, canals etc years ago over in England and no doubt elsewhere - I have not seen these machines but sounds like it could be another good example of biomimetics - the extraction of a good design from nature?
Regarding trees planted near dams, it's worth remembering not to site certain species too close because of potential problems with falling leaves blanketing the surface and adversely affecting aquatic life.
How you might balance this consideration with the practicalities of feeding fruit to fish from overhanging branches I don't know.
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